Complete or partial rupture of the cranial cruciate ligament (CCL) is a common injury of the canine stifle. It is thought that mechanical loading leading to degenerative changes can be a factor in rupture under normal physiologic conditions, but likely it is a multi-factorial etiology. CCL injury causes cranial translation of the tibia relative to the femur resulting in hind limb lameness and often leads to osteoarthritis. It has been demonstrated that dogs with CCL deficient stifles cannot prevent cranial translation of the tibia either by altering hind limb gait or muscle forces across the stifle. As such, conservative treatment of CCL injury is generally unsuccessful. The majority of surgeons would agree that surgical stabilization is the preferred method of treatment. Numerous surgical techniques have been developed including placement of intra-articular grafts, insertion of suture material and/or advancement of periarticular structures outside the joint (extracapsular), and tibial osteotomies that alter joint mechanics. The objective of this presentation is to report the technique and outcome of two novel techniques for treatment of CCL injury. The Cora Based Leveling Osteotomy (CBLO) is based on the normal curvature of the canine tibia (aCORA) and application of principles of deformity correction in man. The SwiveLock Isometric Extra-articular stabilization is based on placement of products designed for rotator cuff repair in man at near isometric sites.
Radiographic measurements are used to determine the location of the normal anatomic CORA. Briefly, the proximal tibial anatomic axis and distal tibial anatomic axis are determined through radiographic measurements. The intersection of these two axes lines is the anatomic CORA. A proximal medial tibial approach exposes the metaphysis or the tibia. Radiographic measurements are transferred to the proximal tibia. A dome osteotomy centered at the CORA is completed and the proximal segment rotated to achieve the desired postoperative TPA (9–12 degrees). Stabilization of the osteotomy was achieved with a bone plate and screws augmented with a HCS. Outcome measurements based on a force plate validated questionnaire, attending surgeon examination, 2nd look arthroscopic exam, and radiographic assessment determined the CORA based leveling osteotomy to be a valuable technique for treatment of cranial cruciate ligament injury.
Isometric Knotless SwiveLock Stabilization: Knotless SwiveLock Anchor
This system is recommended for use in dogs greater than 10 kg. Available sizes are the 3.5-mm, 4.75-mm, and 5.5-mm SwiveLocks. The 4.75-mm and the 5.5-mm SwiveLocks are loaded with 2-mm FiberTape and used for dogs weighing 20 kg and 40 kg; the 3.5-mm SwiveLock is commonly loaded with #5 FiberWire or 2-mm FiberTape and used for dogs/cats 8 kg to 20 kg. The femoral site is located at the level of the distal pole of the lateral fabella. Make a vertical incision through the capsular tissue to expose the joint line between the lateral fabella and caudal margin of the lateral femoral condyle. The proper position is 3–4 mm distal to the lateral fabella-femoral joint line as far caudal as possible in the lateral femoral condyle without engaging articular cartilage. The 4.1 mm spade tip drill bit is used to drill the femoral tunnel to the appropriate depth in the femoral condyle. The femoral tunnel is tapped with the hand tap to cut threads in the bone that will accommodate the anchor and FiberTape (note there is no hand tap for the 3.5 mm SwiveLock). Palpate and locate the protuberance caudal to the extensor groove; this is the site for placement of the tibial tunnel. At the caudal protuberance, beginning as proximal as is possible on the tibial plateau without entering the joint, insert a 0.045 K-wire from lateral to medial. The K-wire is directed to glide caudal to the extensor groove to exit at the medial cortex of the proximal tibia. With the K-wire in position, place a 2-mm cannulated drill bit over the wire and drill a tunnel to exit at the medial cortex. Leave the drill bit in place and remove the K-wire. Through the cannulated hole in the drill bit, place a nytinol Arthrex suture passer such that the loop.
Note: The nytinol suture aid is placed in the tibial tunnel such that the loop is positioned medial. The FiberTape is passed through the 2mm button and then loaded into the suture passer to be pulled through the tibial tunnel from medial to lateral. Once the free ends of the FiberTape exit laterally, they are loaded into the eye of the SwiveLock anchor. Next, the eye of the SwiveLock anchor and FiberTape suture are placed into the femoral tunnel (2–3 mm deep). Eliminate excessive craniocaudal laxity leaving 2–3 mm normal laxity by tensioning each limb of the FiberTape separately. When satisfactory stability is achieved, the limbs of the FiberTape are aligned adjacent to and parallel to the shaft of the SwiveLock. A mark is made on the FiberTape where the limbs of the FiberTape intersect the distal end of the anchor. The eye of the SwiveLock is retracted from the tunnel and the FiberTape pulled back through the eye so that the mark is located within the eye of the SwiveLock. The eye is now re-inserted into the tunnel in preparation for advancement and elimination of cranial laxity. Note at this point there is "slack" in the FiberTape; this will be eliminated and the FiberTape will have the tension developed in each arm as determined above once the eye is seated into the femoral tunnel. To seat the eye, a mallet used to drive the eye to the depth of the femoral tunnel. The Swivelock is advanced such that the bottom of SwiveLock PEEK anchor is flush with the bone. The square flange on the shaft is held and the teardrop knob turned clockwise to engage the anchor. The anchor is advanced into the femoral tunnel until the top of the anchor is flush with the bone surface. The strand of Fiberwire used to hold the eye in place is unwrapped from the teardrop knob and the SwiveLock insertion handle is removed. One arm of the Fiberwire (used to hold the Eye) is pulled to remove the Fiberwire and the Fiberwire suture discarded. The FiberTape is now cut flush to the bone as it exits the PEEK anchor. Tissues are lavaged and the caudal arthrotomy sutured with non-absorbable suture. The fascia lata is advanced and sutured to the patella tendon. The remaining soft tissue closure is performed as the surgeon prefers.